U.S. patent application number 16/768516 was filed with the patent office on 2020-10-15 for coating compositions.
This patent application is currently assigned to Hewlett-Packard Development Company, L.P.. The applicant listed for this patent is Hewlett-Packard Development Company, L.P.. Invention is credited to Tao CHEN, Beverly CHOU, Jesse DAWN, Fereshteh KHORRAMI.
Application Number | 20200324535 16/768516 |
Document ID | / |
Family ID | 1000004905435 |
Filed Date | 2020-10-15 |
United States Patent
Application |
20200324535 |
Kind Code |
A1 |
KHORRAMI; Fereshteh ; et
al. |
October 15, 2020 |
COATING COMPOSITIONS
Abstract
The present disclosure is drawn to coating compositions that can
include an inorganic pigment, a non-ionic surfactant, latex
particles, a polyvinyl alcohol, and a cationic fixing agent. The
inorganic pigment can be included in an amount from 60 wt % to 90
wt % by dry weight. The latex particles can include a
styrene-butadiene copolymer, and can be present in an amount of 4
wt % to less than 10 wt % by dry weight. The polyvinyl alcohol can
have a weight average molecular weight of 150,000 Mw to 400,000
Mw.
Inventors: |
KHORRAMI; Fereshteh; (San
Diego, CA) ; CHOU; Beverly; (San Diego, CA) ;
CHEN; Tao; (San Diego, CA) ; DAWN; Jesse; (San
Diego, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hewlett-Packard Development Company, L.P. |
Spring |
TX |
US |
|
|
Assignee: |
Hewlett-Packard Development
Company, L.P.
Spring
TX
|
Family ID: |
1000004905435 |
Appl. No.: |
16/768516 |
Filed: |
March 9, 2018 |
PCT Filed: |
March 9, 2018 |
PCT NO: |
PCT/US2018/021688 |
371 Date: |
May 29, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B32B 2553/00 20130101;
B32B 2255/12 20130101; B32B 3/28 20130101; C08K 13/02 20130101;
C08K 2201/019 20130101; B32B 29/06 20130101; C09D 1/00 20130101;
B32B 29/08 20130101; B32B 2255/26 20130101 |
International
Class: |
B32B 29/06 20060101
B32B029/06; C09D 1/00 20060101 C09D001/00; B32B 3/28 20060101
B32B003/28; B32B 29/08 20060101 B32B029/08 |
Claims
1. A coating composition, comprising: from 60 wt % to 90 wt % by
dry weight inorganic pigment; a non-ionic surfactant; latex
particles in an amount of 4 wt % to less than 10 wt % by dry
weight, wherein the latex particles comprise a styrene-butadiene
copolymer; a polyvinyl alcohol having a weight average molecular
weight of 150,000 Mw to 400,000 Mw; and a cationic fixing
agent.
2. The coating composition of claim 1, wherein the inorganic
pigment is present in an amount from 70 wt % to 90 wt % by dry
weight, the polyvinyl alcohol is present in an amount from 1 wt %
to 4 wt % by dry weight, and the cationic fixing agent is present
in an amount from 6 wt % to 15 wt % by dry weight.
3. The coating composition of claim 1, wherein the polyvinyl
alcohol is present in an amount from 1 wt % to 2 wt % by dry
weight.
4. The coating composition of claim 1, further comprising a second
polyvinyl alcohol having a weight average molecular weight of
20,000 Mw to 130,000 Mw in an amount from 0.5 wt % to 2 wt % by dry
weight.
5. The coating composition of claim 1, wherein the
styrene-butadiene copolymer of the latex particles is a
carboxylated styrene-butadiene copolymer.
6. The coating composition of claim 1, wherein the coating
composition does not comprise a plastic pigment or a wax.
7. The coating composition of claim 1, wherein the non-ionic
surfactant comprises a fatty alcohol polyglycol ether.
8. A coated liner for corrugated packaging, comprising: a base
liner; and a coating layer on the base liner, the coating layer
including: an inorganic pigment, a non-ionic surfactant, latex
particles in an amount of 4 wt % to less than 10 wt % by dry weight
wherein the latex particles comprise a styrene-butadiene copolymer,
a polyvinyl alcohol having a weight average molecular weight of
150,000 Mw to 400,000 Mw, and a cationic fixing agent.
9. The coated liner of claim 8, wherein the coated liner is
attached a fluted medium opposite a backing liner.
10. The coated liner of claim 8, wherein the coating layer has a
coat weight of 4 gsm to 20 gsm.
11. The coated liner of claim 8, wherein the coating layer is a
single coating layer without a second coating layer applied
thereon.
12. The coated liner of claim 8, wherein the inorganic pigment is
present in an amount from 70 wt % to 90 wt % by dry weight, the
polyvinyl alcohol is present in an amount from 1 wt % to 4 wt % by
dry weight, and the cationic fixing agent is present in an amount
from 6 wt % to 15 wt % by dry weight with respect to the weight of
the coating layer.
13. A method of formulating a coating composition, comprising:
dispersing from 60 wt % to 90 wt % by dry weight, with respect to a
final dry weight of the coating composition, of inorganic pigment
in water with a non-ionic surfactant to form a pigment dispersion;
mixing latex particles into the pigment dispersion, wherein the
latex particles are included in an amount from 4 wt % to less than
10 wt % by dry weight with respect to the final weight of the
coating composition, and wherein the latex particles comprise a
styrene-butadiene copolymer; mixing a polyvinyl alcohol into the
pigment dispersion, wherein the polyvinyl alcohol has a weight
average molecular weight of 150,000 Mw to 400,000 Mw; and mixing a
cationic fixing agent into the pigment dispersion after mixing in
the latex particles and the polyvinyl alcohol therein.
14. The method of claim 13, wherein the inorganic pigment is
included in an amount from 70 wt % to 90 wt % by dry weight, the
polyvinyl alcohol is included in an amount from 1 wt % to 4 wt % by
dry weight, and the cationic fixing agent is included in an amount
from 6 wt % to 15 wt % by dry weight, based on the final dry weight
of the coating composition.
15. The method of claim 14, wherein a rate of addition of the
cationic fixing agent into the mixture is slower than rates of
addition of the latex particles and the polyvinyl alcohol.
Description
BACKGROUND
[0001] Corrugated linerboard or containerboard packaging is often
used as a packaging material. This cellulose fiber-based material
includes a fluted medium bonded to one or two flat liner paper
faces. The fluted medium and the liner paper are usually made of
Kraft pulp. In a typical manufacturing process for corrugated
paperboard packaging materials, the fluted medium is first formed
by heating and moistening a sheet of corrugating medium and then
forming the flute pattern in the sheet using geared wheels. The
fluted medium is then bonded using an adhesive to one sheet of
liner paper for single-faced corrugated linerboard, or between two
sheets of liner paper for double-faced corrugated linerboard or
containerboard
[0002] Liners for corrugated containerboard are often Kraft brown
liners, bleached liners, or white top liners. Printing on the
liners is often performed using offset or flexographic printing
processes before or after the containerboard has been
corrugated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] Additional features of the disclosure are set forth in the
detailed description which follows, taken in conjunction with the
accompanying drawings, which together illustrate, by way of
example, features of the present technology.
[0004] FIG. 1 is a cross-sectional view of an example coated base
liner, as well as a schematic showing assembly with a fluted medium
and backing liner to form a corrugated packaging assembly in
accordance with an example of the present disclosure;
[0005] FIG. 2 is a cross-sectional view of an example coated liner
after printing in accordance with an example of the present
disclosure; and
[0006] FIG. 3 is a flowchart of an example method of formulating a
coating composition in accordance with the present disclosure.
[0007] Reference will now be made to several examples that are
illustrated herein, and specific language will be used herein to
describe the same. It will nevertheless be understood that no
limitation of the scope of the disclosure is thereby intended.
DETAILED DESCRIPTION
[0008] The present disclosure is drawn to coating compositions for
corrugated packaging liners. In one example, a coating composition
can include inorganic pigment, a non-ionic surfactant, latex
particles, a polyvinyl alcohol, and a cationic fixing agent. The
inorganic pigment can be included in an amount from 60 wt % to 90
wt % by dry weight. The latex particles can include a
styrene-butadiene copolymer, and can be included in an amount of 4
wt % to less than 10 wt % by dry weight. The polyvinyl alcohol can
have a weight average molecular weight of 150,000 Mw to 400,000 Mw.
In further examples, the inorganic pigment can be included in an
amount from 70 wt % to 90 wt % by dry weight. The polyvinyl alcohol
can be included in an amount from 1 wt % to 4 wt % by dry weight.
The cationic fixing agent can be present in an amount from 6 wt %
to 15 wt %. In a further example, the polyvinyl alcohol can be
included in the coating composition in an amount from 1 wt % to 2
wt % by dry weight. In another example, the coating composition can
also include a second polyvinyl alcohol having a weight average
molecular weight of 20,000 Mw to 130,000 Mw in an amount from 0.5
wt % to 2 wt % by dry weight. In another example, the
styrene-butadiene copolymer of the latex particles can be a
carboxylated styrene-butadiene copolymer. In yet another example,
the coating composition may not include a plastic pigment or a wax.
In a further example, the non-ionic surfactant can be a fatty
alcohol polyglycol ether.
[0009] In another example, a coated liner for corrugated packaging
can include a base liner and a coating layer on the base liner. The
coating layer can include an inorganic pigment, a non-ionic
surfactant, latex particles, a polyvinyl alcohol, and a cationic
fixing agent. The latex particles can include a styrene-butadiene
copolymer, and can be present in an amount of 4 wt % to 10 wt % by
dry weight. The polyvinyl alcohol can have a weight average
molecular weight of 150,000 Mw to 400,000 Mw. In one specific
example, the coated liner can be attached a fluted medium opposite
a backing liner. In another example, the coating layer can have a
coating weight of 4 gsm to 20 gsm. In other examples, the coating
layer can be a single coating layer without a second coating layer
applied thereon. In further examples, the inorganic pigment can be
present in the coating layer in an amount from 70 wt % to 90 wt %
by dry weight. The polyvinyl alcohol can be present in an amount
from 1 wt % to 4 wt % by dry weight. The cationic fixing agent can
be present in an amount from 6 wt % to 15 wt % by dry weight.
[0010] The present disclosure also extends to methods of
formulating coating compositions. In one example, a method of
formulating a coating composition can include dispersing an
inorganic pigment in water and non-ionic surfactant to form a
pigment dispersion. The amount of inorganic pigment can be from 60
wt % to 90 wt % by dry weight with respect to a final weight of the
coating composition The water can be admixed first, followed by the
non-ionic surfactant, or both can be added at the same time, or the
non-ionic surfactant can be added first followed by the water.
Latex particles can then be mixed into the pigment dispersion. The
latex particles can include a styrene-butadiene copolymer and can
be included in an amount from 4 wt % to less than 10 wt % by dry
weight with respect to the final weight of the coating composition.
A polyvinyl alcohol can also be mixed into the pigment dispersion
(before or after the latex particles, or at the same time). The
polyvinyl alcohol can have a weight average molecular weight of
150,000 Mw to 400,000 Mw. A cationic fixing agent can be mixed into
the pigment dispersion after the latex particles and the polyvinyl
alcohol. The method can include mixing the inorganic pigment in an
amount from 70 wt % to 90 wt % by dry weight. The polyvinyl alcohol
can be included in an amount from 1 wt % to 4 wt % by dry weight.
The cationic fixing agent can be included in an amount from 6 wt %
to 15 wt % by dry weight. In another example, the cationic fixing
agent can be added to the mixture at a rate that is slower than
rates of addition of the latex particles and the polyvinyl
alcohol.
[0011] In certain examples, the coated liners described herein can
be printed upon using inkjet printing. The coating composition can
form an ink receiving coating layer on the liner to increase the
image quality of images printed on the liner. In many cases,
commercial or industrial inkjet printing presses can include fixed
printheads and a moving media web to achieve high speed printing,
e.g., digital printing press or other high speed printers, such as
the HP T400S Web Press.RTM. or the HP T1100 Web Press.RTM., which
can print at rates from 100 feet per minute to 1,000 feet per
minute. Inkjet printheads can use several methods of forming ink
droplets, such as forcing ink through nozzles using thermal
ejection, piezoelectric pressure, or redirecting a continuous
stream of droplets in continuous inkjet printing. Such inkjet
presses can often be used to print images and text on coated liners
and the printed liners can then be used to make packaging materials
such as corrugated cardboard boxes and so on. In other examples,
the coated liners described herein can be printed upon using other
printing methods such as offset printing or flexographic
printing.
[0012] The coating compositions and coated liners described herein
can provide good image quality and mechability of images printed on
the coated liners. As used herein, "mechability" refers to the
ability of a printed medium to go through harsh mechanical
processes such as being wound on rollers, stacked with other media,
rubbing, and so on without damaging the printed image. In many
cases, a coated liner as described herein can be fed through a
series of rollers with varying levels of hygiene and dryers at
various speeds and temperatures. Depending on the speed at which
the liner is fed through the printer and dryers, the drying time
may be short. In some cases ink that has not dried can be
transferred off the liner onto hot rollers, which can degrade image
quality. Although overprint varnish can be added to a printed liner
to protect the printed image, the printed liner can still be
subject to harsh environments before application of the overprint
varnish. Therefore, the coating compositions described herein can
be useful for providing good mechability to the printed image even
before the overprint varnish is applied.
[0013] As used herein, "image quality" can encompass several
specific image properties, such as coalescence, optical density,
bleeding, gloss, and so on. The coating compositions described
herein can provide particularly good coalescence. Ink coalescence
occurs when ink droplets do not absorb sufficiently into the
surface of a medium and the droplets then coalesce one with
another. This coalescence results in an undesirable non-uniform
appearance of the printed ink. Thus, good image quality can include
a low level of coalescence.
[0014] In some examples, the coating compositions described herein
can include a high molecular weight polyvinyl alcohol, such as
polyvinyl alcohol having a weight average molecular weight of
150,000 Mw to 400,000 Mw. The high molecular weight polyvinyl
alcohol can be used instead of a lower molecular weight polyvinyl
alcohol, e.g., from 20,000 Mw to 130,000 Mw, in whole or in part.
In some cases, coating compositions for packaging liners may
include latexes and crosslinkers to increase mechability. However,
the high molecular weight polyvinyl alcohols described herein can,
in some examples, allow for a reduction in the amount of latex used
and a reduction or elimination of the crosslinker used. Because
latex and crosslinkers can sometimes be unpredictable and have
negative impacts on coating compositions, removing the crosslinker
and reducing the amount of latex can provide a coating composition
that is more consistent with less negative effects. Furthermore, in
some examples a smaller amount of high molecular weight polyvinyl
alcohol can be used compared to the amount of low molecular weight
polyvinyl alcohol that can achieve comparable mechability
levels.
[0015] In addition to providing good mechability, the coating
compositions described herein can also provide low levels of ink
coalescence. The coating can absorb and fix ink quickly, which can
prevent ink droplets from coalescing on the surface of the coated
liner. In some examples, including a styrene butadiene latex and a
cationic fixing agent in the coating composition can contribute to
good coalescence levels. In other examples, a plastic pigment and a
wax may be used to increase durability of the printed image.
However, removing the plastic pigment and wax can help to reduce
coalescence. The coating compositions described herein can provide
adequate durability without the plastic pigment or wax, and this
can also provide low levels of coalescence.
[0016] In various examples, a coating composition can include an
inorganic pigment. In some examples, the inorganic pigment can
include calcined clay, modified calcium carbonate, fine or
ultra-fine ground calcium carbonate (GCC), precipitated calcium
carbonate (PCC), or combinations thereof. In one example, the
inorganic pigment can include calcined clay, modified calcium
carbonate (MCC), ultra-fine ground calcium carbonate (GCC),
precipitated calcium carbonate (PCC), or combinations thereof. In
another example, the inorganic pigment can include calcined clay,
modified calcium carbonate (MCC), ultra-fine ground calcium
carbonate (GCC), or combinations thereof.
[0017] In one example, the inorganic pigment can include the
calcined clay KAOCAL.RTM. from Thiele Kaolin Company (Sandersville,
Ga.) having a particle size distribution of about 83-92% particles
finer than 2 .mu.m. In further examples, the inorganic pigment can
include ground calcium carbonate such as Hydrocarb.RTM. 60 (a fine
ground calcium carbonate having a solids content of about 74% and a
median diameter of about 1.4 .mu.m) or Hydrocarb.RTM. 90 (an
ultrafine ground calcium carbonate having a solids content of about
76% and a median diameter of about 0.7 .mu.m), both available from
Omya North America (Cincinnati, Ohio).
[0018] In further examples, the inorganic pigment can be ground
calcium carbonate; or a mixture of calcined clay and fine ground
calcium carbonate; or a mixture of calcined clay and ultrafine
ground calcium carbonate; or a mixture of calcined clay and fine
ground and ultrafine ground calcium carbonate. In one example, the
mixture can contain, by dry weight, at least about 50% of fine
and/or ultrafine ground calcium carbonate. In certain examples, the
inorganic pigment of the coating composition can include an
ultrafine ground calcium carbonate (having a median particle size
of about 0.7 .mu.m), calcined clay (having a particle size
distribution of about 83-92% particles finer than 2 .mu.m), and/or
a combination thereof.
[0019] In some examples, the inorganic pigment can have a median
particle size ranging from about 0.5 .mu.m to about 5 .mu.m. In
another example, the inorganic pigment can have a median particle
size ranging from about 0.5 .mu.m to about 2 .mu.m. In still other
examples, the inorganic pigment can have a median particle size
ranging from about 0.75 .mu.m to about 2 .mu.m, or a median
particle size ranging from about 0.5 .mu.m to about 1 .mu.m. As
used herein, "particle size" refers to the diameter of a
substantially spherical particle (i.e., a spherical or
near-spherical particle having a sphericity of >0.84), or the
average diameter of a non-spherical particle (i.e., the average of
multiple diameters across the particle).
[0020] In certain examples, the inorganic pigment can be present in
the coating composition in an amount ranging from about 60 wt % to
about 90 wt % or from about 70 wt % to about 90 wt % by dry weight
based on the total dry weight of the coating composition.
[0021] The coating compositions described herein can also include a
non-ionic surfactant. As used herein, "non-ionic surfactant" refers
to a surfactant that does not have an ionic charge at the
hydrophilic end of the surfactant molecule. In certain examples,
the non-ionic surfactant can include an ethopropoxylated
polyarylphenol, an ethoxylated tristyrylphenol, a fatty alcohol
polyglycol ether, or a combination thereof. Specific examples of
non-ionic surfactants can include Soprophor.RTM. 796/p from Solvay;
Soprophor.RTM. S/25 from Solvay; Dehypon.RTM. E, Dehypon.RTM. GRA,
Dehypon.RTM. KE or Dehypon.RTM. WET, Disponil.RTM. AFX 4030 or
4050, or Plurafac.RTM. LF 7319 (all from BASF Corp.).
[0022] In certain examples, the non-ionic surfactant can be present
in an amount from 0.01 wt % to 2 wt % by dry weight based on the
total dry weight of the coating composition. In further examples,
the non-ionic surfactant can be present in an amount from 0.05 wt %
to 1 wt % by dry weight, or from 0.1 wt % to 0.5 wt % by dry
weight.
[0023] The coating compositions can also include latex particles.
The latex particles can include a styrene-butadiene copolymer. As
used herein, the term "latex" refers to a polymer that is capable
of being dispersed in an aqueous medium. The latex may act as a
binder in the coating composition. In an example, the latex can be
present in the coating composition in an amount ranging from 4 wt %
to less than 10 wt % by dry weight based on the total dry weight of
the coating. In another example, the latex can be present in an
amount from 6 wt % to 8 wt % by dry weight.
[0024] In certain examples, styrene-butadiene latex particles can
be present together with another type of latex particle. In further
examples, the latex particles can include a styrene-butadiene
copolymer together with another polymer or copolymer. In various
examples, additional polymers, copolymers, and types of latex
particles can be formed from monomers such as vinyl monomers,
allylic monomers, olefin monomers, unsaturated hydrocarbon
monomers, or combinations thereof.
[0025] Classes of vinyl monomers can include vinyl aromatic
monomers (e.g., styrene), vinyl aliphatic monomers (e.g.,
butadiene), vinyl alcohols, vinyl halides, vinyl esters of
carboxylic acids (e.g., vinyl acetate), vinyl ethers, (meth)acrylic
acid, (meth)acrylates, (meth)acrylamides, (meth)acrylonitriles, or
mixtures of two or more of the above, for example. The term "(meth)
acrylic latex" can include polymers of acrylic monomers, polymers
of methacrylic monomers, and copolymers of the aforementioned
monomers with other monomers.
[0026] Examples of vinyl aromatic monomers that may be included can
include styrene, 3-methylstyrene, 4-methylstyrene,
styrene-butadiene, p-chloromethylstyrene, 2-chlorostyrene,
3-chlorostyrene, 4-chlorostyrene, divinyl benzene, vinyl
naphthalene and divinyl naphthalene. Vinyl halides can include, for
example, vinyl chloride and vinylidene fluoride. Vinyl esters of
carboxylic acids can include, for example, vinyl acetate, vinyl
butyrate, vinyl methacrylate, vinyl 3,4-dimethoxybenzoate, vinyl
maleate and vinyl benzoate. Examples of vinyl ethers can include
butyl vinyl ether and propyl vinyl ether.
[0027] In some examples, the coating composition can include a
styrene-butadiene based latex and no other latex may be
present.
[0028] In certain examples, the coating composition can include a
styrene-butadiene based latex such as Litex.RTM. PX 9710,
Litex.RTM. 9720, Litex.RTM. 9730 or Litex.RTM. PX 9740, from
Synthomer (Essex, UK). Additional latex types that may be added can
include Gencryl.RTM. 9525, Gencryl.RTM. 9750, and Gencryl.RTM.
9780, from Omnova; STR 5401, from Dow Chemical Company (Midland,
Mich.), or combinations thereof. In one example, the
styrene-butadiene based latex can be carboxylated, e.g., Litex.RTM.
PX 9740.
[0029] As mentioned above, in some examples the coating composition
can include a high molecular weight polyvinyl alcohol having a
weight average molecular weight of 150,000 Mw to 400,000 Mw. In
further examples, the polyvinyl alcohol can have a weight average
molecular weight of 190,000 Mw to 400,000 Mw. The polyvinyl alcohol
can also act as a binder in addition to the latex mentioned above.
In certain examples, the high molecular weight polyvinyl alcohol
can be present in an amount from 1 wt % to 4 wt % by dry weight. In
further examples, the high molecular weight polyvinyl alcohol can
be present in an amount from 1 wt % to 2 wt % by dry weight. In
some examples, depending on the other ingredients that may be
present, the mechability of the coating compositions can be further
increased by including a high molecular weight polyvinyl alcohol,
such as polyvinyl alcohol having a weight average molecular weight
of 150,000 Mw to 400,000 Mw. The high molecular weight polyvinyl
alcohol can be used instead of a lower molecular weight polyvinyl
alcohol, in whole or in part. In some cases, coating compositions
for packaging liners may include latexes and cross-linkers to
increase mechability as well. However, the higher molecular weight
polyvinyl alcohols described herein can, in some examples, allow
for a reduction in the amount of latex used and a reduction or
elimination of the cross-linker used. Because latex and
cross-linkers can sometimes be unpredictable and have negative
impacts on coating compositions, removing the cross-linker and
reducing the amount of latex can provide a coating composition that
may be more consistent with less negative effects. Furthermore, in
some examples, a low molecular weight polyvinyl alcohol, e.g.,
20,000 Mw to 130,000 Mw, can be used along with the high molecular
weight polyvinyl alcohol to adjust mechability levels. Thus, there
can be a wide variety of polyvinyl alcohol molecular weights that
can be used, including low molecular weight PVA, e.g., 20,000 Mw to
130,000 Mw admixed with high molecular weight PVA, e.g., 150,000 Mw
to 400,000 Mw; or the high molecular PVA without other PVA
molecular weight material. For example, a low molecular weight
polyvinyl alcohol can be present at from 0.5 wt % to 3 wt % or from
0.5 wt % to 2 wt %, and a high molecular weight polyvinyl alcohol
can be present at from 0.5 wt % to 3 wt % or from 0.5 wt % to 2 wt
%. In another example, the total amount of polyvinyl alcohol,
including both the high molecular weight and the low molecular
weight polyvinyl alcohol, can be from 1 wt % to 6 wt % by dry
weight.
[0030] In some examples, the high molecular weight polyvinyl
alcohol can include Mowiol.RTM. 40-88 (205,000 Mw), Mowiol.RTM.
56-88 (195,000 Mw), and Poval.TM. 235 (precise molecular weight is
unknown, but has a viscosity of 95 mPas, which corresponds to a
molecular weight in the range of 150,000 Mw to 400,000 Mw), each
from Kuraray (Houston, Tex.). In further examples, lower molecular
weight polyvinyl alcohols can include Mowiol.RTM. 4-98 (27,000 Mw),
Mowiol.RTM. 4-88 (31,000 Mw), Mowiol.RTM. 6-98 (47,000 Mw), and
Mowiol.RTM. 18-88 (130,000 Mw), each from Kuraray (Houston,
Tex.).
[0031] The coating composition can also include a cationic fixing
agent. In some examples, the cationic fixing agent can include
water-soluble mono-valent metallic salts or water-soluble
multi-valent metallic salts, where the metallic salt includes (i) a
cation of a metal such as a Group I metal, Group II metal, Group
III metal, transition metal, or combination thereof, and (ii) an
anion such as chloride, iodide, bromide, nitrate, sulfate, sulfite,
phosphate, chlorate, acetate, chlorohydrate, and combinations
thereof. Some examples of the cation can include sodium, calcium,
copper, nickel, magnesium, zinc, barium, iron, aluminum, chromium,
or combinations thereof. Some examples of the cationic fixing agent
can include calcium chloride, magnesium chloride, calcium bromide,
magnesium bromide, calcium nitrate, magnesium nitrate, aluminum
chlorohydrate, or combinations thereof. In one example, the
cationic fixing agent can be calcium chloride (CaCl.sub.2).
[0032] In certain examples, the cationic fixing agent may be
present in the coating composition in an amount ranging from 6 wt %
to 15 wt % by dry weight based on the total dry weight of the
coating composition.
[0033] In some examples, a reaction may take place between the
cationic fixing agent and an anionic pigment in the ink (applied to
the coated liner) to fix the anionic pigment. As such, image
quality (e.g., bleed, coalescence, text quality, etc.) can be
affected by the cationic fixing agent. In some examples, ink can be
printed onto the coated liners described herein without applying
any additional fixer fluid because the cationic fixing agent in the
coating of the coated liner is sufficient to fix pigments in the
ink.
[0034] In some cases, coating compositions may include plastic
pigments to enhance gloss and/or durability. However, in some
examples, the coating compositions described herein can be devoid
of plastic pigments. In other examples, a plastic pigment may be
present in the coating composition in an amount no greater than 0.1
wt % by dry weight. In some examples, removing the plastic pigment
can reduce ink coalescence, resulting in better image quality. In
certain examples, plastic pigments can include styrene based
pigments and/or hollow sphere type polystyrene based pigments. In
some examples, the plastic pigment can include Ropaque.TM. AF1055
from Dow Chemical, or Lytron.TM. HG80 from Omnova Solutions
Inc.
[0035] In further examples, the coating composition may be devoid
of wax particles. Some coating compositions may include wax
particles to provide scratch and rub resistance, but in some
examples the coating compositions described herein can achieve
adequate scratch and rub resistance without wax particles. Removing
the wax particles can also provide reduced ink coalescence. In
further examples, the coating composition may contain wax particles
in an amount no greater than 0.1 wt % by dry weight. In some
examples, wax particles can include polypropylene wax, polyethylene
wax, polytetrafluoroethylene wax, and the like. The polyethylene
wax may be a high density wax or a low density wax. Examples of
waxes can include Ultralube.RTM. D806 available from Keim-additec
Surface GmbH (Kirchberg, Germany), Liquilube.TM. 405 from Lubrizol
Advanced Materials, Inc., and waxes available from Micro Powders,
Inc.
[0036] Beyond the coating compositions themselves, the present
disclosure also extends to coated liners. In various examples, the
coated liner can include a base liner and a coating applied to the
base liner. The coating can be formed by applying the coating
compositions described herein and allowing the coating to dry. The
coating can be applied by any coating technique suitable for
coating compositions having a viscosity of about 400 cp to 3,000
cp, such as blade coating or rod coating. In one example, the
viscosity can be form about 600 cp to about 1800 cp, or in another
example, from about 800 cp to about 1200 cp.
[0037] In certain examples, the coating layer on the coated liner
can have a coat weight of 4 gsm to 20. In other examples, the
coating layer can have a coat weight of 5 gsm to 15 gsm. In further
examples, the coating layer can be formed as two separate layers
that are coated consecutively to form a coating layer. In other
examples, the coating layer can be formed as a single coating layer
with a single application of the coating composition.
[0038] Any suitable type of base liner can be used to make the
coated liners described herein. In certain examples, the base liner
can be a Kraft liner, a white top liner, or a bleached liner. Kraft
linerboard is typically brown, while white top liner board includes
a white top surface on top of a brown Kraft base. Bleached liner
board can be bleached white all the way through. Base liners can be
defined as the liner material on corrugated packaging that is
typically used for printing and/or labeling. A backing liner, on
the other hand, can be defined as a liner that is used on the
opposite side of a fluted medium to provide the corrugated packing
structure on both sides of the fluted medium, e.g., the backing
liner on one side and the base liner on the other side. In the
context of the present disclosure, the base liner is the liner that
is coated with the coating compositions described herein which
provides a suitable surface for printing thereon, such as by inkjet
printing. As a note, the backing liner can be modified similarly
with a coating composition applied thereto as well, particularly
when there may be utility to printing on both sides of the
corrugated packaging.
[0039] In the case of white top liners, a white top liner can be
made with a clay coating or a layer of white fibers on the top to
produce a white appearance. In one example, bleached white fibers
can be layered over brown fibers to make a white top liner.
Uncoated white top liners can be made with a paper machine having
multiple headboxes or otherwise capable of laying down multiple
layers of fiber. The combination of layers of brown fibers with
bleached white fibers can produce a stronger liner than all
bleached fibers, and the cost can be reduced because the brown
fibers are cheaper than bleached fibers.
[0040] In some examples, the coating composition described herein
can be applied during the manufacturing process of the base liner.
For example, the coating composition can be applied to a pulp of
the base liner when the pulp includes more than 90% solids. The
pulp and the coating composition can then be dried to remove liquid
from the base liner and the coating layer, forming the coated
liner. In other examples, a pre-made dry base liner can be coated
with the coating composition.
[0041] FIG. 1 shows a cross-sectional view of an example coated
base liner 100 in accordance with an example of the present
disclosure. The coated base liner includes a base liner 110 and a
coating layer 120 on or applied to the base liner. In one example,
the coated liner can be assembled as corrugated packaging by
attaching the base liner to a fluted medium 160, which is also
attached to a backing liner 170. The backing liner can be
positioned opposite the base liner. In some examples, the fluted
medium can be formed by pressing a moistened linerboard between
geared wheels to form the fluting pattern. The fluted medium can
then be glued between the coated liner and the backing liner. In
certain examples, the backing liner can also be coated with the
coating composition if printing on the backing liner is desired. In
other examples, the corrugated packaging may be in the form of a
box and the backing liner may be oriented toward the inside of the
box where printing on the backing liner would not be visible. In
such examples, the backing liner can be uncoated. The corrugated
packing can also be arranged in other configurations suitable for
packaging.
[0042] In certain examples, additional layers can be added to the
coated liner during and after the printing process. For example, in
some cases a layer of ink can be printed onto the coating layer to
form a printed image, followed by a layer of overprint varnish to
protect the printed image. In other examples, a curl control layer
may be added to the back surface of the base liner to reduce
curling of the printed liner. FIG. 2 shows an example coated liner
200 having a base liner 210, a coating layer 220, an ink layer 230,
and overprint varnish layer 240, and a curl control layer 250. In
certain examples, the curl control layer can include a starch. In
further examples, the overprint varnish layer can include an
overprint varnish such as Inxkote.RTM. AC911 or Inxkote.RTM. AC9116
from INX International; Aquaflex.RTM. H.R. from Flint Group; or
Thermagloss.RTM. 1394E, Thermagloss.RTM. 426, Thermagloss.RTM. 425,
Thermagloss.RTM. 475, Thermagloss.RTM. 460, or Digiguard.RTM. gloss
100 from Michelman. The fluted medium and backing liner are not
shown in this example, but could be incorporated or attached to
this coated liner similarly as that shown in FIG. 1.
[0043] FIG. 3 shows a flowchart of an example method 300 of
formulating a coating composition. The method includes dispersing
310 from 60 wt % to 90 wt % by dry weight, with respect to a final
dry weight of the coating composition, of inorganic pigment in
water and non-ionic surfactant to form a pigment dispersion; mixing
320 latex particles into the pigment dispersion, wherein the latex
particles are included in an amount from 4 wt % to less than 10 wt
% by dry weight with respect to the final weight of the coating
composition, and wherein the latex particles include a
styrene-butadiene copolymer; mixing 330 a polyvinyl alcohol into
the pigment dispersion, wherein the polyvinyl alcohol has a weight
average molecular weight of 150,000 Mw to 400,000 Mw; and mixing
340 a cationic fixing agent into the mixture after mixing in the
latex particles and the polyvinyl alcohol. In certain examples, the
rate of addition of the cationic fixing agent into the mixture can
be slower than the rates of addition of the latex particles and the
polyvinyl alcohol.
[0044] It is noted that, as used in this specification and the
appended claims, the singular forms "a," "an," and "the" include
plural referents unless the content clearly dictates otherwise.
[0045] As used herein, the term "about" is used to provide
flexibility to a numerical range endpoint by providing that a given
value may be "a little above" or "a little below" the endpoint. The
degree of flexibility of this term can be dictated by the
particular variable and can be determined based on experience and
the associated description herein.
[0046] The term "coated liner(s)" can refer to coated base liners
in accordance with the present disclosure, and in some specific
instances can also include coated backing liners.
[0047] As used herein, a plurality of items, structural elements,
compositional elements, and/or materials may be presented in a
common list for convenience. However, these lists should be
construed as though each member of the list is individually
identified as a separate and unique member. Thus, no individual
member of such list should be construed as a de facto equivalent of
any other member of the same list solely based on their
presentation in a common group without indications to the
contrary.
[0048] Concentrations, dimensions, amounts, and other numerical
data may be presented herein in a range format. It is to be
understood that such range format is used merely for convenience
and brevity and should be interpreted flexibly to include the
numerical values explicitly recited as the limits of the range, and
also to include all the individual numerical values or sub-ranges
encompassed within that range as if each numerical value and
sub-range is explicitly recited. For example, a weight ratio range
of about 1 wt % to about 20 wt % should be interpreted to include
the explicitly recited limits of 1 wt % and about 20 wt %, and also
to include individual weights such as 2 wt %, 11 wt %, 14 wt %, and
sub-ranges such as 10 wt % to 20 wt %, 5 wt % to 15 wt %, etc.
[0049] As a further note, in the present disclosure, it is noted
that when discussing the coating compositions, coated liners, and
methods of formulating coating compositions, each of these
discussions can be considered applicable to each of these examples,
whether or not they are explicitly discussed in the context of that
example. Thus, for example, in discussing details about the coating
compositions, such discussion also refers to the methods and the
coated liners described herein, and vice versa.
EXAMPLES
Example 1--Comparison of Polyvinyl Alcohols
[0050] A series of coating compositions 1-8 were formulated with
the compositions shown in Table 1 based on dry parts by weight. As
shown in the table, the coating compositions included identical
ingredients with the exception of the polyvinyl alcohol. The
polyvinyl alcohol was varied by including multiple different types
of polyvinyl alcohol in multiple different amounts in the coating
compositions. The particular polyvinyl alcohols used in these
examples had the trade name Mowiol.RTM.. The Mowiol.RTM. polyvinyl
alcohols are identified according to their viscosity and their
degree of hydrolysis. In the name of polyvinyl alcohol, Mowiol.RTM.
is followed by two numbers. The first number is the viscosity in
mPas of a 4% aqueous solution of the polyvinyl alcohol at
20.degree. C. The second number is the degree of hydrolysis. These
polyvinyl alcohols are manufactured by hydrolyzing polyvinyl
acetate, and the degree of hydrolysis refers to the percentage of
acetate groups that have been hydrolyzed to alcohol groups.
[0051] The molecular weight of the polyvinyl alcohol correlates to
the viscosity of the polyvinyl alcohol solutions. In these
particular examples, the polyvinyl alcohols have the following
weight average molecular weights: Mowiol.RTM. 4-98: 27,000 Mw;
Mowiol.RTM. 6-98: 47,000 Mw; Mowiol.RTM. 18-88: 130,000 Mw;
Mowiol.RTM. 40-88: 205,000 Mw; Mowiol.RTM. 56-88: 195,000 Mw.
[0052] The coating compositions were coated on a white top liner at
a coat weight of 15 gsm and the mechability was ranked. The
mechability rankings were found by printing a strip of violet made
by combining magenta and cyan ink at a coat weight of 15 gsm onto
the coated liner. The ink was dried at 375.degree. F. for 3 seconds
and then an aluminum roller heated to 100.degree. C. was rolled
directly over the print for three passes. Moving the roller back
and forth counted as one pass. The results were then visually
compared. The mechability was ranked based on the frequency of ink
removal spots and the visual damage to the print strip. A higher
mechability ranking indicates better mechability, with 5 being the
best ranking. The results show that examples 3 and 4 had the best
mechability with 4 parts by dry weight of Mowiol.RTM. 18-88 and
Mowiol.RTM. 40-88. A coating composition with 4 parts by weight of
Mowiol.RTM. 56-88 was also tested (not shown in table) and also
scored 5 on the mechability test. Examples 6-8 show that when the
amount of polyvinyl alcohol is reduced to 2 parts by dry weight,
the Mowiol.RTM. 40-88 and Mowiol.RTM. 56-88 provide good
mechability while the Mowiol.RTM. 18-88 provides poorer
mechability.
TABLE-US-00001 TABLE 1 Coating Composition Nos. (Dry parts by
weight) Ingredients 1 2 3 4 5 6 7 8 Hydrocarb .RTM. 90 80 80 80 80
80 80 80 80 Kaocal .RTM. 20 20 20 20 20 20 20 20 Disponil .RTM. AFX
4050 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Litex .RTM. PX9740 8 8 8 8 8 8
8 8 Mowiol .RTM. 4-98 (27,000 Mw) 4 -- -- -- -- -- -- -- Mowiol
.RTM. 6-98 (47,000 Mw) -- 4 -- -- 2 -- -- -- Mowiol .RTM. 18-88
(130,000 Mw) -- -- 4 -- -- 2 -- -- Mowiol .RTM. 40-88 (205,000 Mw)
-- -- -- 4 -- -- 2 -- Mowiol .RTM. 56-88 (195,000 Mw) -- -- -- --
-- -- -- 2 CaCl.sub.2 7 7 7 7 7 7 7 7 Mechability Ranking: 2 2 5 5
1.5 3 4 5 Hydrocarb .RTM. 90 is ultrafine ground calcium carbonate
from Omya North America; Kaocal is a calcined clay from Thiele
Kaolin Company; Disponil .RTM. 4030 AFX is a fatty alcohol
polyglycol ether surfactant from BASF; Litex .RTM. PX9740 is a
styrene butadiene-based latex from Synthomer; and Mowiol .RTM.
polymers are polyvinyl alcohols from Kuraray.
Example 2--Decreasing Amount of Polyvinyl Alcohol
[0053] A similar experiment was performed with the coating
compositions 9-15 shown in Table 2 based on dry parts by weight. In
this example, the coating compositions were coated as a two layer
coating, with each of the two layers having a coat weight of 10 gsm
for a total coat weight of 20 gsm. The same mechability test was
then performed as in Example 1. These examples also shown that
Mowiol.RTM. 40-88 and Mowiol.RTM. 56-88 provide better mechability
when the amount of polyvinyl alcohol is reduced to 2 or 3 parts by
dry weight.
TABLE-US-00002 TABLE 2 Coating Composition Nos. (Dry parts by
weight) Ingredients 9 10 11 12 13 14 15 Hydrocarb .RTM. 90 80 80 80
80 80 80 80 Kaocal .RTM. 20 20 20 20 20 20 20 Disponil .RTM. AFX
4050 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Litex .RTM. PX9740 8 8 8 8 8 8 8
Mowiol .RTM. 6-98 (47,000 Mw) 4 2 -- -- -- -- -- Mowiol .RTM. 18-88
(130,000 Mw) -- -- 3 -- 2 -- -- Mowiol .RTM. 40-88 (205,000 Mw) --
-- -- 3 -- 2 -- Mowiol .RTM. 56-88 (195,000 Mw) -- -- -- -- -- -- 2
CaCl.sub.2 7 7 7 7 7 7 7 Mechability Ranking: 2 1.5 4 5 3 4 5
Example 3--Mixtures of High and Low Molecular Weight Polyvinyl
Alcohol
[0054] A similar experiment was performed with the coating
compositions 16-19 shown in Table 3 based on dry parts by weight.
Example 19 includes the polyvinyl alcohol Poval.TM. 235. The
molecular weight of Poval.TM. 235 was unknown, but the viscosity
was 95 mPas, which corresponds to a molecular weight in the range
of 150,000 Mw to 400,000 Mw. In this example, the coating
compositions were coated as a two layer coating, with each of the
two layers having a coat weight of 10 gsm for a total coat weight
of 20 gsm. The same mechability test was then performed as in
Example 1.
TABLE-US-00003 TABLE 3 Coating Composition Nos. (Dry parts by
weight) Ingredients 16 17 18 19 Hydrocarb .RTM. 90 80 80 80 80
Kaocal .RTM. 20 20 20 20 Disponil .RTM. AFX 4050 0.3 0.3 0.3 0.3
Litex .RTM. PX9740 8 8 8 8 Mowiol .RTM. 6-98 (47,000 Mw) 4 1 1 1
Mowiol .RTM. 18-88 (130,000 Mw) -- 2 -- -- Mowiol .RTM. 40-88
(205,000 Mw) -- -- 2 -- Poval .TM. 235 * -- -- -- 2 CaCl.sub.2 7 7
7 7 Mechability Ranking: 2 4 5 5 * Poval .TM. 235 is available from
Kuraray. The molecular weight of Poval .TM. 235 was unknown, but
the viscosity was 95 mPa s, which corresponds to a molecular weight
in the range of 150,000 Mw to 400,000 Mw.
[0055] It can be seen from Tables 1-3 that the mechability tends to
be better with polyvinyl alcohols having a weight average molecular
weight from 150,000 to 400,000 as well as with increasing amounts
of polyvinyl alcohol. However, when polyvinyl alcohol of 150,000 to
400,000 Mw is used, a smaller amount can be used to achieve better
mechability than a larger amount of the polyvinyl alcohol having a
molecular weight below 150,000 Mw. Additionally, a mixture of
polyvinyl alcohol having a molecular weight of 20,000 Mw to 130,000
Mw with a polyvinyl alcohol having a molecular weight of 150,000 to
400,000 can be used achieve good mechability as shown in examples
18 an 19.
Example 4--Type of Latex
[0056] A separate experiment was performed to compare two
styrene-butadiene based latexes: Litex.RTM. PX9740 (available from
Synthomer plc) and XZ 94378 (available from Trinseo UK Limited).
Styrene-butadiene based latexes were selected as binders for the
present coating compositions because of their cohesive and adhesive
strength, flexibility, durability, and dimensional stability
properties. They are also effective for use with coating
compositions with high solids or filler content, and can provide
good coalescence. As the compositions of the present disclosure
include from 60 wt % to 90 wt % inorganic pigment,
styrene-butadiene polymer latex can be used effectively compared to
other types of latexes, such as some acrylic latexes, for
example.
[0057] Two coating compositions (20 and 21) were formulated having
the compositions shown in Table 4. These coatings were coated at a
coat weight of 15 gsm on a white top liner. The coalescence of ink
printed on the coatings was tested using the following procedure.
Squares of ink ranging in ink density from 4% to 100% were printed
in a strip on the coated liners. Cyan ink was selected because the
chosen cyan ink tends to show the worst visible coalescence. After
a 5 or 30 second drying time under a 375.degree. F. dryer, the
strip was scanned and analyzed using software to calculate the
coalescence in each square of the strips. The square with the
highest coalescence value was reported to measure coalescence
differences between the two coating compositions. The lower
coalescence values are better (i.e., less coalescence). A
difference of about 0.3 to 0.5 is noticeable to the naked eye.
TABLE-US-00004 TABLE 4 Coating Composition Nos. (Dry parts by
weight) Ingredients 20 21 Hydrocarb .RTM. 90 80 80 Kaocal .RTM. 20
20 Disponil .RTM. AFX 4030 0.3 0.3 Litex .RTM. PX9740* 8 -- XZ
94378 -- 8 Mowiol .RTM. 6-98 (47,000 Mw) 4 4 CaCl.sub.2 7 7
Coalescence Value: 2 2.7 XZ 94378 is a styrene-butadiene copolymer
available from Trinseo UK Limited; *Litex .RTM. PX9740 includes a
carboxylated styrene-butadiene copolymer.
[0058] It can be seen from Table 4 that when all other ingredients
are the same, both styrene-butadiene based latex provided
acceptable coalescence. The Litex.RTM. PX9740, which includes a
carboxylated styrene-butadiene copolymer, provided the best
coalescence out of the two latexes tested. These formulations did
not include a high molecular weight polyvinyl alcohol, but rather
were formulated to evaluate coalescence provided by the
latexes.
Example 5--Plastic Pigment and Wax
[0059] A separate experiment was performed to evaluate the effect
of plastic pigment and wax particles. Coating compositions 22-25
were formulated with the compositions shown in Table 5 based on dry
parts by weight. These coating compositions were then coated on
both white top and bleached liners at a coat weight of 10 gsm. The
coalescence of ink printed on the coated liners was then tested
using the procedure of Example 4.
TABLE-US-00005 TABLE 5 Coating Composition Nos. (Dry parts by
weight) Ingredients 22 23 24 25 Hydrocarb .RTM. 90 80 80 80 80
Kaocal .RTM. 20 20 20 20 Dispex .RTM. N-40V 0.3 0.3 0.3 0.3 Litex
.RTM. PX9740 10 10 10 10 Mowiol .RTM. 4-98 (27,000 Mw) 5 4 1.25 1
Ultralube .RTM. D806 -- 2 -- 2 Rhopaque .RTM. AF 1055 -- 6 -- 6
CaCl.sub.2 5 5 5 5 Coalescence (Bleached Liner) 3.5 4.3 3 4.3
Coalescence (White Top Liner) 2.7 3.9 2.5 3.6 Ultralube .RTM. D806
is a wax available from Keim-additec Surface GmbH; and Rhopaque
.RTM. AF 1055 are styrene acrylic hollow sphere polymeric
pigments.
[0060] It can be seen from Table 5 that the coalescence was better
in each case when the wax (Ultralube.RTM. D806) and the plastic
pigment (Rhopaque.RTM. AF 1055) were not included. These
formulations did not include a high molecular weight polyvinyl
alcohol, but rather were formulated to evaluate the impact of wax
and/or plastic pigment on coalescence.
Example 6--Corrugated Packaging Assembly
[0061] A fluted medium, such as that shown at 160 in FIG. 1, is
prepared by pressing a moistened linerboard between laterally
elongated geared wheels to form a fluting pattern. The fluted
medium is glued between a backing liner and a base liner coated
with one of Coating Composition Nos. 3, 4, 6-8, 11-15, 17-19 The
backing liner may or may not also be coated with one of a coating
composition of the present disclosure or some other coating
composition. The corrugated packaging, now assembled, can be
further configured in the form of a box with the backing liner
oriented toward the inside of the box.
[0062] While the disclosure has been described with reference to
certain examples, various modifications, changes, omissions, and
substitutions can be made without departing from the spirit of the
disclosure. It is intended, therefore, that the disclosure be
limited by the scope of the following claims.
* * * * *